Maharashtra HSC Fish Processing Technology (Bifocal) key terms

The stiffening of fish muscle after death caused by loss of ATP and irreversible binding of actin and myosin filaments. Its onset and duration depend on species, temperature and handling, and it affects fillet texture and water loss.

The post-mortem sequence in which adenosine triphosphate in muscle is consumed and degraded through ADP, AMP, inosine and hypoxanthine. Its speed rises with temperature and rough handling, and the products are used as freshness indicators.

Filleting or freezing fish before rigor mortis sets in, while muscle is still flexible. It avoids gaping and shrinkage from cutting a stiffened carcass, but the product must be stabilized quickly to prevent contraction on thawing.

The separation of muscle blocks along connective tissue seams so that slits appear in fillets. It is worsened by rough handling, delayed chilling, pre-rigor filleting and freezing, and it lowers grade and yield.

A freshness index calculated as the percentage of ATP breakdown products inosine and hypoxanthine relative to total ATP-related compounds. Values near zero indicate very fresh fish; higher values indicate progressive loss of freshness.

The amount of volatile amines, mainly trimethylamine and ammonia, released as fish spoils, expressed in milligrams per 100 grams of flesh. It is a widely used chemical measure of spoilage, with limits set by national standards.

A volatile amine with a fishy odour formed when bacteria reduce trimethylamine oxide in fish muscle. Its build-up is a classic sign of spoilage, especially in marine species, and is measured as part of quality testing.

A naturally occurring compound in marine fish and elasmobranchs that helps balance osmotic pressure in tissues. Bacteria use it as an electron acceptor, converting it to trimethylamine and causing spoilage odours.

Microorganisms that grow on fish after death and break down proteins and other compounds, producing off-odours, slime and discolouration. Their growth is controlled mainly by temperature, hygiene and available water.

The continuous sequence of chilling, cold storage and refrigerated transport that keeps fish between catch and consumption within a safe temperature range. Any break in the chain shortens shelf life and raises spoilage risk.

Cooling fish rapidly with crushed or flake ice, usually in insulated boxes with drainage, to bring flesh close to zero degrees Celsius. Proper icing slows bacterial growth and enzyme activity and keeps the product firm and fresh.

Damage to fish tissue caused by cooling too fast or to too low a temperature without freezing, or by direct contact with ice and melt water. It can cause surface discolouration, softening and drip loss.

The fluid released from fish tissue when it is thawed or cut, mainly due to cell damage from freezing and handling. High drip loss reduces yield, appearance and eating quality and indicates poor freezing practice.

Localised drying and oxidation of frozen fish surfaces caused by sublimation of ice in poorly wrapped or fluctuating storage conditions. It appears as white, dry patches and causes toughness and off-flavour.

Coating frozen fish with a thin layer of ice by dipping or spraying with water so that surface moisture is protected. The glaze limits oxidation and dehydration during frozen storage and is declared in net weight rules.

Holding fish at temperatures well below freezing, typically minus eighteen degrees Celsius or lower, to stop microbial growth and slow quality changes. Temperature stability and packaging determine how long quality is retained.

The period during which a fish product keeps acceptable safety, taste, texture and appearance under stated storage conditions. It is established by testing and is printed on the label as a best-before or use-by date.

The date after which a perishable fish product must not be sold or eaten because safety may be compromised. It differs from a best-before date, which concerns quality rather than safety.

A food safety system that identifies biological, chemical and physical hazards, sets control points with limits, and requires monitoring and corrective action. Fish processors use it to manage risks from receiving through storage and dispatch.

A step in a food process where a control measure can be applied to prevent, eliminate or reduce a significant hazard to an acceptable level. Each point has measurable limits and a defined monitoring frequency.

Basic hygiene and operational conditions such as cleaning, pest control, water quality and staff health that must be in place before a hazard analysis system can work. They support, but do not replace, critical control points.

The set of documented practices covering premises, equipment, personnel, sanitation and process control that a fish processing unit must follow to produce safe, wholesome food consistently.

A written procedure describing how and when cleaning and sanitising of equipment, surfaces and utensils is done, including chemicals, concentrations and verification. It is a core part of hygiene control in a processing plant.

Water that meets drinking-water safety standards and is fit for contact with fish, ice, equipment and hands. Its quality is checked regularly because contaminated water can introduce pathogens into products.

The weight of edible fillet obtained from a whole fish, usually expressed as a percentage of the original weight. It varies with species, size, processing method and skill, and directly affects profitability.

Processing fish into products with higher market worth than whole or minimally handled fish, such as fillets, breaded portions, canned or smoked items. It raises income but requires investment in facilities and quality control.

A washed, minced fish paste made from white-fleshed species, stabilized with cryoprotectants and used to make imitation seafood products. Washing removes fat, pigments and enzymes, and the gel-forming ability is critical.

A substance such as sorbitol or sucrose added to minced fish or surimi to protect proteins from denaturation during frozen storage. It helps retain water-binding and gel-forming ability after thawing.

A protein-rich powder made by cooking, pressing, drying and grinding fish or fish waste. It is used mainly in animal feed and its quality depends on protein content, fat level and freshness of raw material.

Oil recovered from fish or fish waste, rich in long-chain omega-3 fatty acids and used in feed, supplements and industrial products. Oxidation during storage is its main quality problem and is controlled by antioxidants and cool storage.

The development of unpleasant flavours and odours from oxidation of fats in fish and fish products. It is accelerated by oxygen, light, heat and certain metals and is limited by antioxidants and protective packaging.

A liquid product made by liquefying fish or fish waste with acids or by fermentation, used as feed ingredient. It preserves protein and is a low-cost way to use by-catch and processing waste.

Preserving fish by applying dry salt or brine so that water activity falls and spoilage organisms are inhibited. The rate of salt uptake and the final salt content determine texture, keeping quality and product type.

Removing moisture from fish by sun, air or mechanical means to lower water activity and slow spoilage. Control of temperature, humidity and airflow prevents case hardening and spoilage during the process.

A measure of the free moisture available in a food for microbial growth, expressed on a scale from zero to one. Lowering it by salting or drying is a principal way to preserve fish.

A preservation method in which fish is sealed in a can or retort pouch and heat-sterilized to destroy spoilage organisms and pathogens. Correct process time and temperature are essential for commercial sterility.

A pressure vessel used to heat-seal and sterilize canned or pouched fish at temperatures above boiling point. Uniform heat distribution and recorded process schedules are necessary to achieve a safe product.

The condition in which a canned or retorted product is free of microorganisms capable of growing under normal storage conditions, including pathogens of concern. It is achieved by a validated heat process.

Treating fish with smoke from burning wood, often after salting, to add flavour and colour and to extend shelf life. The effect comes from drying, antimicrobial smoke components and lowered water activity.